The Intermountain Seismic Belt (ISB)

Utah's Earthquakes are Part of a Bigger Picture

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What is......

The Intermountain Seismic Belt??

Earthquakes in the Intermountain West Region


The Intermountain Seismic Belt (ISB) is a zone of earthquake activity that runs north-south through the Intermountain West from northwestern Montana in the North, through Wyoming, Idaho, and Utah, and southern Nevada/northern Arizona to the south. Click here for a map of earthquake locations that define the Intermountain Seismic Belt.

If you compare this earthquake activity with other earthquake zones in the United States, you will see this belt of activity connects to that of southern California. Although the Intermountain Seismic Belt is not as active as southern California, the maps shows that there is a high level of earthquake activity all along its length.

Most earthquakes in the ISB are shallow, occuring at depths less than 12 miles (20 km) and there have been 50 moderate-to-large (magnitude 5.5 to 7.5) earthquakes in this zone since 1900. The two largest earthquakes were the 1959 Hebgen Lake, Montana earthquake (Mag=7.5) and the 1983 Borah Peak, Idaho earthquake (Mag = 7.3).



Based on research conducted by the University of Utah Seismograph Stations, the Utah Geological Survey, and the United States Geological Survey